During building construction projects, such as the interior construction phase of a large new building under construction, or during renovation of an older building, it is useful to refer to Building Information Modeling (BIM) data. This data, when available, defines the building structure, including the interior, in three dimensions, and its use increases the productivity of construction workers by facilitating the location and placement of various building construction elements and fixtures. Typically, the BIM model of the building is maintained after the building construction is completed, and can be used over the life of the building for renovation, expansion, and maintenance purposes. The BIM model defines building geometry, spatial relationships, and quantities and properties of building components.
It is extremely useful to be able to locate quickly various construction points within the building interior. As the interior of a building is being finished, connectors, anchors and the like are attached to ceilings on each floor, and cuts are made and holes drilled in the ceilings using power saws and drills. All of this must be accomplished at predetermined, precisely defined positions in the building ceilings. For example, nail guns, power saws, powder anchor tools, and the like may be used to nail, cut, install fasteners, and perform other operations at predetermined points within the building with little error. Additionally, a large number of electrical, plumbing, and HVAC components must be properly sited and installed. The construction points for all of these building elements must be located with some precision. Typically, work on the ceilings of buildings is performed by a worker on a scissor lift device having an operator support platform and a powered scissor mechanism that raises and lowers the platform. The scissor lift device may be powered and drivable by a worker on the platform such that it can be moved about the building without the platform being lowered. Typically, a substantial amount of time and effort has been required to lay out the many construction points on the building ceiling. Teams of workers have been needed to measure and mark predetermined locations. Performing this task has been tedious and subject to errors, resulting both from measurement mistakes and from accumulated errors. Further, the cost of the layout process, and the time needed to perform the layout process have both been significant.
Layout of the construction points at a building interior construction site has been accomplished in more automated ways, such as for example by using a robotic total station device. The total station is positioned at a fixed, known location and directs a beam of laser light to a desired location. The beam may illuminate a floor, ceiling or wall at a point or may be directed to, and reflected from a target, such as a retroreflective target. By measuring the time of travel of the beam from the total station to the surface or target and then back to the total station, the distance to the target is determined. The direction of the beam to the target is also known. Since the position of the total station is known, the position of the target can easily be determined. It is desirable, however, to be able to layout a number of construction points on a building ceiling and to be able to do so for a worker on a scissor lift or similar device.